1. Field of the Invention
This invention relates to a pressure regulator for reducing an unregulated pressure of an introduced high-pressure gas and obtaining a predetermined regulated pressure, which pressure regulator is suitable for use in liquefied gas utilizing appliances, gas supply facilities, and the like, and particularly for stabilization of fuel supply to solid oxide type fuel cells (SOFC's) and solid polymer type fuel cells (PEFC's).
2. Description of the Related Art
Ordinarily, liquefied gases and ordinary high-pressure gases, which have been accommodated in, for example, gas cylinders, have very high unregulated pressures and cannot be utilized directly. Also, the unregulated pressures of the liquefied gases and the ordinary high-pressure gases fluctuate markedly due to factors, such as an ambient temperature and a residual gas quantity. Therefore, pressure regulators (or pressure governors) for reducing the pressures of the high-pressure gases have heretofore been utilized widely in liquefied gas utilizing appliances, gas supply facilities, and the like. The pressure regulators have structures, wherein a regulated pressure is detected by a diaphragm, a regulating valve capable of moving in accordance with a displacement of the diaphragm is operated such that the regulated pressure becomes equal to a predetermined pressure in cases where the unregulated pressure fluctuates, and the predetermined regulated pressure is thereby obtained. (A pressure regulator having the structure described above is described in, for example, Patent Literature 1.)
The pressure regulators having various structures designed in accordance with required operating ranges of unregulated pressures, required response characteristics, and required stability have been used in practice. In accordance with the quality required of the regulated pressure, one kind of a pressure regulator or a combination of several kinds of pressure regulators has heretofore been used, and the predetermined regulated pressure has thus been obtained.
Fundamental structures of ordinary pressure regulators will be described hereinbelow with reference to FIGS. 15A, 15B, and 15C. FIGS. 15A, 15B, and 15C are schematic views showing fundamental structures of ordinary pressure regulators. FIG. 15A is a schematic view showing a single-valve type pressure regulator. With reference to FIG. 15A, a pressure regulator 500 comprises a diaphragm 504, which partitions a region within a casing 501 into a pressure regulating chamber 502 and an atmospheric chamber 503. The pressure regulator 500 also comprises a gas introducing port 505, through which a high-pressure gas having a pressure before being regulated is introduced into the pressure regulator 500. The pressure regulator 500 further comprises a regulating valve 506, which is interlocked with the diaphragm 504. The regulating valve 506 opens and closes an aperture 506c, through which the gas introducing port 505 and the pressure regulating chamber 502 communicate with each other. The regulating valve 506 performs the operations for opening and closing the aperture 506c from the unregulated pressure side and thereby reduces and regulates the unregulated pressure to the regulated pressure. The pressure regulator 500 still further comprises a gas discharging port 508, through which the gas having the regulated pressure and having passed through the pressure regulating chamber 502 is discharged. The pressure regulator 500 also comprises a weight 509, which urges the diaphragm 504 toward the direction of opening of the regulating valve 506 and thereby sets the regulated pressure.
The pressure regulator 500 is based upon the detection of a pressure difference between the atmospheric pressure and the regulated pressure. Specifically, the force occurring from an area of the diaphragm 504 and the pressure difference between the atmospheric pressure and the regulated pressure acts toward the direction of closing of the regulating valve 506, and the gravity of the weight 509 acts toward the direction of opening of the regulating valve 506. In a state in which the force occurring from the area of the diaphragm 504 and the pressure difference between the atmospheric pressure and the regulated pressure and the gravity of the weight 509 are balanced with each other, the regulated pressure is kept at the set pressure. In cases where the pressure on the gas discharging side, i.e. the regulated pressure in the pressure regulating chamber 502, is higher than the set pressure, the diaphragm 504 is displaced toward the side of the atmospheric chamber 503, and the regulating valve 506 is operated in the direction that closes the aperture 506c. In cases where the regulated pressure in the pressure regulating chamber 502 is lower than the set pressure, the diaphragm 504 is displaced toward the side of the pressure regulating chamber 502, and the regulating valve 506 is operated in the direction that opens the aperture 506c. More specifically, the motion of the diaphragm 504 occurring from the detection of the aforesaid pressure difference between the atmospheric pressure and the regulated pressure is transmitted to the regulating valve 506, which is located on the gas introducing side, and the regulated pressure is kept at the predetermined pressure through the pressure regulation performed with the opening and closing operations of the regulating valve 506.
However, in the cases of the single-valve type pressure regulator 500 described above, a pressure loss occurs due to the gas stream flowing through the regulating valve 506, and the force that displaces the diaphragm 504 toward the side of the atmospheric chamber 503, i.e. the force acting in the direction that closes the regulating valve 506, arises excessively from the value of the pressure loss described above and the area of the regulating valve 506. As described above, the regulating valve 506 performs the operations for opening and closing the aperture 506c from the unregulated pressure side. Therefore, in cases where the unregulated pressure becomes high, the aforesaid excessive force acting in the direction that closes the regulating valve 506 becomes large. Accordingly, the problems occur in that, as the unregulated pressure becomes high, the regulated pressure becomes low little by little, and the gas stream is ceased with the passage of time.
FIG. 15B is a schematic view showing a duplex-valve type pressure regulator. With reference to FIG. 15B, a pressure regulator 600 comprises a diaphragm 604, which partitions a region within a casing 601 into a pressure regulating chamber 602 and an atmospheric chamber 603. The pressure regulator 600 also comprises a gas introducing port 605, through which a high-pressure gas having a pressure before being regulated is introduced into the pressure regulator 600. The pressure regulator 600 further comprises two regulating valves 606 and 607, which are interlocked with the diaphragm 604. The regulating valves 606 and 607 respectively open and close two apertures 606c and 607c, through which the gas introducing port 605 and the pressure regulating chamber 602 communicate with each other. The regulating valves 606 and 607 thus reduce and regulate the unregulated pressure to the regulated pressure. The pressure regulator 600 still further comprises a gas discharging port 608, through which the gas having the regulated pressure and having passed through the pressure regulating chamber 602 is discharged. The pressure regulator 600 also comprises a weight 609, which urges the diaphragm 604 toward the direction of opening of the regulating valve 606 and thereby sets the regulated pressure.
The two regulating valves 606 and 607 described above are located such that the regulating valve 606 performs the operations for opening and closing the aperture 606c, which communicates with the pressure regulating chamber 602, from the unregulated pressure side, and such that the regulating valve 607 performs the operations for opening and closing the aperture 607c from the regulated pressure side. Therefore, with the duplex-valve type pressure regulator 600, the force due to the pressure loss occurring at the regulating valve 606 and the force due to the pressure loss occurring at the regulating valve 607 act in reverse directions and cancel each other. Accordingly, the drop of the regulated pressure accompanying the increase in the unregulated pressure is capable of being compensated for, and the regulated pressure is capable of being kept at a predetermined pressure.
As described above, the duplex-valve type pressure regulator 600 has good performance. However, the duplex-valve type pressure regulator 600 has the problems in that the two regulating valves 606 and 607 cannot always be located appropriately. Even if the two regulating valves 606 and 607 are capable of being located such that the regulating valves 606 and 607 simultaneously come into contact with their valve seats, the pressure loss of the gas stream passing through the regulating valve 606 and the pressure loss of the gas stream passing through the regulating valve 607 cannot always be equal to each other. Therefore, it is not always possible to constitute the duplex-valve type pressure regulator 600 such that the force exerted by the unregulated pressure upon the regulating valve 606 and the force exerted by the unregulated pressure upon the regulating valve 607 are perfectly canceled with each other.
FIG. 15C is a schematic view showing a modified duplex-valve type pressure regulator. With reference to FIG. 15C, a pressure regulator 700 comprises a diaphragm 704, which partitions a region within a casing 701 into a pressure regulating chamber 702 and an atmospheric chamber 703. The pressure regulator 700 also comprises a gas introducing port 705, through which a high-pressure gas having a pressure before being regulated is introduced into the pressure regulator 700. The pressure regulator 700 further comprises a regulating valve 706, which is interlocked with the diaphragm 704. The regulating valve 706 opens and closes an aperture 706c, through which the gas introducing port 705 and the pressure regulating chamber 702 communicate with each other. The regulating valve 706 thus reduces and regulates the unregulated pressure to the regulated pressure. The pressure regulator 700 still further comprises a regulating member 707, which is constituted of an O-ring and undergoes sliding movement together with the regulating valve 706. The pressure regulator 700 also comprises a gas discharging port 708, through which the gas having the regulated pressure and having passed through the pressure regulating chamber 702 is discharged. The pressure regulator 700 further comprises a weight 709, which urges the diaphragm 704 toward the direction of opening of the regulating valve 706 and thereby sets the regulated pressure.
The regulating valve 706 performs the operations for opening and closing the aperture 706c, which communicates with the pressure regulating chamber 702, from the unregulated pressure side. The unregulated pressure coming from the gas introducing port 705 acts upon one surface of the regulating member 707, which is constituted of the O-ring. Also, the regulated pressure, which comes from the pressure regulating chamber 702 through an intra-plunger gas flow path 710, acts upon the other surface of the regulating member 707. The force due to the pressure difference between the unregulated pressure, which acts upon the one surface of the regulating member 707, and the regulated pressure, which acts upon the other surface of the regulating member 707, is exerted upon the regulating member 707. The force, which is thus exerted upon the regulating member 707, cancels the force occurring from the value of the pressure loss, which arises at the regulating valve 706, and the area of the regulating valve 706. Therefore, even if the unregulated pressure becomes high, the regulated pressure is capable of being kept at the predetermined pressure. With the modified duplex-valve type pressure regulator 700, the regulating member 707 (corresponding to the regulating valve 607 of the duplex-valve type pressure regulator 600 shown in FIG. 15B) is constituted of the O-ring capable of undergoing the sliding movement, and the problems with regard to the location of the two regulating valves 606 and 607 of the duplex-valve type pressure regulator 600 shown in FIG. 15B are thereby solved.
[Patent Literature 1]                Japanese Unexamined Patent Publication No. 8(1996)-303773        
As described above, the single-valve type pressure regulator has a simple structure, but has the problems in that the regulated pressure cannot always be obtained accurately with respect to a wide unregulated pressure range. In order for the regulated pressure to be obtained with respect to a wide unregulated pressure range by use of the single-valve type pressure regulator, it is necessary that a plurality of the single-valve type pressure regulators are utilized in order to reduce the unregulated pressure little by little from the high pressure to an intermediate pressure and from the intermediate pressure to a low pressure. However, in such cases, the advantages of the single-valve type pressure regulator with regard to the simple structure is lost. Also, in cases where the plurality of the single-valve type pressure regulators are connected to one another, it is necessary that the load for pressure regulation in the pressure regulator located on the upstream side, i.e. the pressure regulator for the high pressure, is set to be large. However, in such cases, follow-up characteristics with respect to marked fluctuations in pressure cannot be kept good.
The duplex-valve type pressure regulator described above theoretically has good performance. However, the duplex-valve type pressure regulator has the problems in that the two regulating valves cannot always be located appropriately, and therefore the duplex-valve type pressure regulator cannot always be used in practice.
The modified duplex-valve type pressure regulator described above has practicality, but has the problems described below. Specifically, since the value of the pressure loss occurring at the regulating valve varies in accordance with the gas flow rate, it is substantially impossible to cancel the force, which is exerted upon the regulating valve, by the force, which is exerted upon the regulating member constituted of the O-ring. Therefore, an error in regulated pressure occurs in accordance with the variation unregulated pressure. Also, since the regulating member (i.e., the O-ring) undergoes the sliding movement in accordance with the variation in unregulated pressure, the frictional resistance at the part of the regulating member is high. Therefore, the problems occur in that the response characteristics of the control of the regulated pressure with respect to the variation in unregulated pressure cannot be kept good. As a result, the pressure regulation with respect to the marked variation in unregulated pressure cannot be kept quick, and the fluctuation in regulated pressure becomes large. In order to cope with the problems described above, ordinarily, a lubricant is imparted to the O-ring sliding section. However, in cases where a gas having high dissolving characteristics is introduced into the modified duplex-valve type pressure regulator, the lubricant is attached by the gas, and the response characteristics of the control of the regulated pressure with respect to the variation in unregulated pressure quickly become bad. Therefore, the use of the lubricant is applicable only to the cases where an inert gas is introduced into the modified duplex-valve type pressure regulator.
Also, in cases where the pressure of the high-pressure gas is reduced and regulated with the pressure regulator provided with the diaphragm, it is desired that the pressure regulation to the regulated pressure having been set is capable of being performed accurately with respect to a wide unregulated pressure range. However, in cases where the regulated pressure is set by the alteration of the pressure regulating load applied to the diaphragm, if the difference between the highest pressure of the unregulated pressure and the set pressure of the regulated pressure is large, the problems will occur in that the accuracy with which the pressure is regulated becomes low.
Specifically, in cases where the degree of pressure reduction with one regulating valve is high, the pressure fluctuation with respect to the fluctuation in degree of opening of the regulating valve becomes large. Therefore, the operation accuracy of the regulating valve and the production accuracy of the valve structure largely affect the accuracy with which the pressure is regulated. However, it is not always possible to obtain a high operation accuracy of the regulating valve and a high production accuracy of the valve structure.
In view of the above circumstances, in one aspect of the present invention, as will be described later, two stages of governor means, i.e. a first-stage governor means comprising a diaphragm and a regulating valve and a second-stage governor means comprising a diaphragm and a regulating valve, are utilized, and the pressure regulation is performed in two stages in order for the pressure regulation accuracy to be enhanced. However, if two stages of governor means are merely located in parallel, the problems will occur in that the size of the pressure regulator cannot be kept small.
Further, actually, the regulating valve performs the pressure reduction with a very narrow valve space. Therefore, ordinarily, at least either one of the valve body and the valve seat of the regulating valve is made from an elastic body, such as a rubber material. However, in such cases, the problems occur in that various kinds of gases other than inert gases cause the elastic body to swell to a certain extent and to suffer from a variation in volume. The variation in volume of the elastic body arises principally in the directions of opening and closing operations of the regulating valve. Therefore, the valve space between the valve body and the valve seat becomes small with the passage of time of use, and the regulated pressure becomes low. In particular, in cases where a gas having high dissolving characteristics, such as a dimethyl ether gas, is introduced into the pressure regulator, it often occurs that the gas flow ceases within several tens of minutes.
Furthermore, in cases where a general-purpose synthetic resin is utilized as the material for a member constituting the pressure regulator, the problems described below occur. Specifically, when the member constituted of a certain kind of a general-purpose synthetic resin is brought into contact with the gas having the high dissolving characteristics, such as a dimethyl ether gas, for a long period of time, gas permeability, corrosion, cracks, and the like, occur with the member, and the member becomes not usable any more.
It is expected that dimethyl ether is usable as a substitute for a liquefied petroleum gas, a fuel for solid oxide type fuel cells (SOFC's), and a fuel for solid polymer type fuel cells (PEFC's). However, dimethyl ether exhibits a large variation in vapor pressure with respect to temperature. For example, in cases where the temperature of the use environment of at most 80° C. is taken into consideration, the vapor pressure of dimethyl ether rises to as high as 2,000 kPa. In cases where the pressure regulation is to be performed with respect to the dimethyl ether gas, it is necessary that the pressure reduction and the pressure regulation are capable of being performed sufficiently with respect to the wide pressure range described above, and that the pressure regulator has a structure resistant to the dissolving characteristics of the dimethyl ether gas.